1. Field of the Invention
The present invention relates generally to liquid pumping and collecting apparatuses, and more particularly to a system for pumping underground liquid, such as groundwater samples, from small diameter wells. It should be noted, however, that the invention is also applicable and adaptable in various other applications that will occur to one skilled in the art from the disclosure herein.
2. Description of the Prior Art
Recent increases in public concern for the environment have resulted in various government-imposed environmental regulations with regard to groundwater quality and land-site cleanup projects. Among such regulations are requirements relating to the monitoring and sampling of water quality of aquifers as sources of drinking water. In response to these requirements, water quality analytic capabilities have been improved and water-sampling equipment has been developed. However, presently most sampling using bladder pumps employs permanently installed dedicated pumps in monitoring wells. Current portable equipment for the groundwater sampling is relatively heavy, bulky, and thus difficult to transport from one monitoring site to another.
One of the preferred types of pumps for groundwater sampling or other pumping applications is a submersible, fluid-actuated pump wherein the actuating fluid is preferably a gas such as compressed air. A flexible bladder member in this type of pump separates and isolates the interior of the pump into two chambers: a liquid chamber that contains the sample fluid and is in communication with both the pump inlet and outlet, and a gas chamber surrounding the first chamber, and connected to a source of the actuating gas, with the bladder disposed therebetween. The pumped liquid is conveyed through the pump by alternately pressurizing and venting or relieving the pressure in the gas chamber to contract and relax the bladder member, thus alternately decreasing and increasing the volume of the liquid chamber. The pumped liquid is drawn into the liquid chamber during such increases in volume under the influence of the natural hydrostatic head of the groundwater or other pumped liquids and is discharged through the pump outlet during such decreases in volume, thereby conveying the pumped liquid through the pump.
The conventional bladder pumps employ ball-type check valves that control flow of liquid trough the pump. However, the ball-type check valves have proven to be not very efficient, especially in low-flow applications where the velocity with which water enters the pump intake is low. Ball members of the check valves are prone to roll around valve seats and, thus are slow to respond to the change of the water flow direction.
The need therefore exists for a liquid sampling bladder pump with more efficient check valves.
The present invention alleviates the drawbacks of the prior art. The present invention provides a pump for a wide variety of applications, including, but not limited to, groundwater quality applications, withdrawing and collecting contaminated groundwater or other subterranean liquids from a landfill-site having a plurality of in-ground wells. The novel pump may be built with a small outside diameter, such as xc2xexe2x80x3 or xe2x85x9exe2x80x3 and is adapted to sample temporarily and/or permanently installed small diameter monitoring wells. The bladder pump of the present invention is particularly effective for conducting xe2x80x9clow-flow samplingxe2x80x9d from monitoring wells where minimal purging is undertaken prior to sample collection. Please note that low-flow refers to the velocity with which water enters pump intake and that is imparted to the formation pore water in the immediate vicinity of the well screen.
The preferred liquid sampling pump is an air-operated, gas-displacement bladder pump having a generally hollow cylindrical body submersible in the in-ground well. The pump body includes a liquid inlet with an inlet cone-shaped check valve for allowing one-way fluid flow from the in-ground well into the housing interior, and a liquid outlet with a similar outlet cone-shaped check valve allowing one-way fluid flow from the pump body interior to the discharge collection equipment. The cone-shaped check valves provide better effectiveness than conventional ball-type check valves.
An exemplary control apparatus in some applications for supplying and controlling an operating fluid for a gas-displacement pump supplies pulses of a pressurized operating fluid, such as air, into the pump body interior in order to forcibly displace and discharge liquid material through the outlet. Between pressurized pulses of the operating fluid, the control apparatus relieves the pressure of the other operating fluid in the pump body interior in order to permit liquid material to flow, under the influence of its own hydrostatic head, into the pump housing through the inlet.